The invention relates to thermal insulation systems and, in particular, to an apparatus for drying built-up or compact roof insulation and wall insulations. Moisture in insulated built-up or compact roofing systems causes many premature roof failures and unwanted energy losses. Such roofing systems are installed on most commercial flat roofs. Typically, the systems are made up of metal, concrete or wood decks supported by heavy wood beams or steel I beams. The decks are covered with vapor barriers upon which the insulation, which is usually provided in board form ranging from 2.times.4 foot to 4.times.8 foot panels, is laid. The insulation in turn is covered with between two to four felt layers and an asphalt coating or a continuous weather barrier.
Moisture can enter the roofing system through minor cracks which may develop at the seams or from weathering. Poorly designed roofs develop ponding which increases the possibility of water intrusion. When the insulation becomes wet, or partly so, the air or gas spaces become filled with water.
Heat transmission through the water-filled spaces approaches the rate of conductivity of water which is over 24 times greater than that of air. Additionally, if the moisture freezes, heat transmission can increase by as much as 90 times the original rate. Moreover, moisture can damage the felt material and cause further structural damage. Approximately three billion square feet of new roofs were installed in 1981 at a cost of about 3.6 billion dollars, of which 75% accounted for reroofing.
The conventional method for attempting to remove moisture from roof insulation is to attempt to seal all the cracks and then employ top relief vents, edge vents, breathing top membranes and the like to permit moisture to evaporate from insulation. However, studies suggest that it is very difficult to dry out wet roof insulation in such a manner. Recent tests conclude that present methods for drying insulation will not work once the insulation contains any appreciable water. Another proposal has been to eliminate the lower vapor barrier in insulation systems so that evaporation can occur at the bottom of the insulation system. This solution will only be effective if the vapors can pass to the building below and can present additional problems if a major task occurs in the insulation system; without a lower barrier, leaking water will also pass unhindered to the building below. Further, the removal of the lower vapor barrier will allow interior moisture to condense in the insulation system. See, generally, Tobiasson et al. "Can Wet Insulation Be Dried Out?", Proceedings of the DOE-ORNL/ASTM Symposium on Thermal Insulation, Materials and Systems (1981), for a further discussion of the unsolved problems of wet roof insulation.
There exists a need for better apparatuses and methods for drying wet insulation, particularly in compact roofing systems. An apparatus which can be applied as a retrofit solution to the problem of wet insulation as well as modified structures for new roofing systems to avoid the problem would satisfy long-felt needs in this industry.
Equally important is the problems of moisture in building walls. If a building is constructed without a carefully installed vapor barrier or insulation is added to the walls of an existing building without a vapor barrier, water vapor penetrates the insulation and the existance of large temperature changes within the insulation causes condensation to occur within the wall cavity. Present efforts in the industry are directed at finding a retrofit insulation which can be installed in an existing wall without major reconstruction and which prevents moisture from penetrating it. Foam insulations which are pumped into the wall cavities have been found to shrink upon curing leaving gaps and cracks for moisture penetration and foams have been suspected of causing interior air pollution. At present there is no widely accepted system for retrofit wall cavity insulation. There exists the need for a reliable method to remove any moisture which condenses in an insulated wall.